Skin and manufacturing method thereof, manufacturing method of skin for air bag door and air bag door

ABSTRACT

The present invention intends to provide an air bag door construction in which the air bag develops smoothly and securely, the skin can be easily produced with small man-hour, and which is excellent in the surface appearance. 
     The skin  50  is formed by a mold  5  including an endless and annular wall  50  provided at a part of a molding surface to be inclined relative to the molding surface. A groove portion  35  of the skin  3  formed by the wall  50  is cut at a bottom portion thereof to separate the skin  3  into a general portion  30  and a door portion  31 . The general portion  30  and the door portion  31  are relatively shifted to make both surfaces thereof flush with each other. 
     When the surfaces of the general portion  30  and the door portion  31  are flush by the relative shift, gap between the general portion  30  and the door portion  31  can be narrowed, and gap appeared on the surface can also be narrowed. Also, when the skin is disposed in the mold for foam forming, the skin can position the general portion  30  and the door portion  31  in the desired position easily, and will not scatter a skin chip in the development of the air bag.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of, and claimspriority under 35 U.S.C. §122, of U.S. application Ser. No. 09/585,276(“the parent application”), filed Jun. 2, 2000, now U.S. Pat. No.6,632,388 whose entirety is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a skin used to form a surface such as avehicle interior panel and manufacturing method thereof, and to amanufacturing method of skin for air bag door and an air bag door.

2. Related Art

For protecting passenger in an automobile from a traffic accident withincrease of the traffic, an air bag has been installed in the recentautomobile. For example, the air bag for a driver contained in asteering wheel is expanded by gas generated due to shock applied incollision of the automobile and developed in to a vehicle room. Thus,the air bag protects the driver seated on a driver's seat from collisionagainst the steering wheel and a front glass. The air bag may also hasbeen contained in a rear surface side of an instrument panel to protecta passenger seated on an assistant seat from collision against theinstrument panel and the front glass. Further, in recent years,installing the air bag in a rear surface side of a door trim to protectthe passenger from collision applied from side (door) has beenrecommended.

The vehicle interior panel such as the instrument panel and the doortrim are constructed by a base member made of a hard resin, a foamedbody layer made of a polyurethane foam etc. and laminated on a surfaceof the base member, and a skin made of a polyvinylchloride etc. andlaminated on a surface of the foamed body layer. The interior panelholds shape thereof by rigidity of the base member, increases smoothfeeling by the foamed body layer, and increases surface appearance andfurther increases the smooth feeling by the skin.

When the air bag is disposed in the rear surface side of such interiorpanel, the interior panel having rigidity is hardly broken to hinder theexpansion and development of the air bag. In view of this, the interiorpanel is provided with an opening usually closed or covered by an airbag door and allows the air bag to develop. When the air bag expands bylarge shock applied to the automobile by collision etc., the air bagdoor is pushed and opened by the air bag for allowing the air bag todevelops into the vehicle room smoothly.

Conventionally, the air bag door is formed separately or independentfrom the interior panel, and is fixed to the interior panel byengagement and so on. According to such separate air bag doorconstruction, the interior panel does not hinder development of the airbag into the vehicle room. However, in this case, a boundary line (outerperiphery) of the air bag door may appear on the surface of the interiorpanel as a relatively wide and deep groove, or a step or heightdifference may be formed between the interior panel surface and the airbag door surface, whereby the surface appearance of the interior panelis deteriorated in both cases.

On the other hand, if the air bag door is formed integral with theinterior panel, the boundary line of the air bag door does not appear orexpose on the surface of the interior panel to improve the surfaceappearance thereof. However, such integral structure may hinderdevelopment of the air bag into the vehicle room, so that connectingstrength of the air bag door with the interior panel needs to beselected as small as possible for an instantaneous development of theair bag when the shock is applied.

As such interior panels having small connecting strength of the air bagdoor, Japanese Patent Publication No. 1-202550 for example discloses acover body for an air bag comprising a core layer made of a hard resinand provided with a slit of H-shape or cross-shape, and a soft skinlayer formed on a surface of the core layer integral therewith.

Also, Japanese Patent Publication No. 5-294196 discloses an air bagcontaining cover body comprised of a hard core layer provided with aslit at a rear surface side thereof, and a soft skin layer.

In these interior panels disclosed in the above Publications, in theusual state when the shock is not applied, rigidity of the interiorpanel is secured by the core layer, and the smooth feeling is obtainedby the skin layer. When the shock is applied, the cover body is tornalong the slit on the core layer forming a fragile portion by theexpanding force of the air bag and allows the air bag to develop intothe vehicle room.

However, even when the fragile portion is provided on the core layer sothat part of the core layer defined by the fragile portion forms thedoor, there is case where an extensive rigidity of the skin layerhinders development of the air bag. In view of this, Japanese PatentPublication No. 7-156737 discloses an air bag structure in which a skinof an air bag door and a skin of an interior panel are separatelyformed, and a convex portion and a concave portion provided on annularbent flanges of the both skins are engaged with each other to form anintegrated skin. This integrated skin is disposed in a mold, followed byan integral forming of a foamed body layer to the skin. This air bagstructure hardly generates a step or a gap at the boundary portion ofthe air bag door, and will not cause problem due to the extensionrigidity of the skin. Japanese Patent Publication No. 11-222089discloses a skin for an instrument panel comprised of a general portionand an air bag door portion formed at a part of the general portion anddefined by an annular groove portion. In this skin, the air bag doorportion and the general portion are formed so that a step portion isformed between the surface of the former and the surface of the latter,and opposing peripheries of the air bag door portion and the generalportion are coincided in a direction parallel to the surface of theskin.

The groove portion of the skin for the instrument panel is deformed byrelative shift of the air bag door portion and the general portion inthe direction orthogonal to the skin surface to remove the step portion,then is set in the foam mold together with the resin base member. Then,the foamed body layer is formed by the foam forming to connect it withthe base member and the skin integrally. Thus, the instrument panelhaving the air bag door can be produced.

According to the skin for the instrument panel of Japanese PatentPublication No. 11-222089, the surface appearance of the skin can beimproved due to the narrowed width of the groove portion. Also, theman-hour for forming the skin for the instrument panel can be reducedsince the skin having the air bag door portion can be formed by singleforming process. Further, durability of the mold for the skin increasessince thickness of the convex portion on the mold for forming the grooveportion needs not be thinned extremely.

However, the above Japanese Patent Publication No. 7-156737 and JapanesePatent Publication No. 11-222089 have following disadvantages. That is,in the interior panel construction shown in the above JP '737, the skinof the air bag door and the skin of the interior panel needs to beseparately formed, which requires the separate, two kinds of molds, andincreases the manufacturing cost of the skin. Also, the connectingworking between the skin of the air bag door with the skin of theinterior panel increases the required man-hour. Further, to preventformation of the step portion and the gap which may be formed at theboundary portion of the air bag door when the air bag door and theinterior panel are connected, the convex portion and the concave portionformed at the annular flanges of the skins should have high positionalaccuracy. To set the tearing condition of the skin in the expansion ofthe air bag constant, the convex portion and the concave portion of theannular flanges should have high shape accuracy. These accuracyrequirements also increase the man-hour.

Also, in the skin for the instrument panel disclosed in the above JP'089, the groove portion has the depth direction extending orthogonal tothe skin surface. For this reason, if the groove portion is opened inthe endurance test or after long-term use, the deeper part of the grooveappears remarkably. Further, the instrument panel is formed in thecondition where the groove portion is deformed, the stress generated bydeformation of the groove portion remains in the skin to causedeformation of the skin.

SUMMARY OF THE INVENTION

The present invention is made by taking above circumstances intoconsideration, and has the first object or purpose to provide a skincomprising a general portion and a defining portion defined by anannular groove portion and produced integrally by small man-hour. Thesurface appearance of the skin is improved by narrowing width of thegroove portion and by removing the step portion between the generalportion and the defined portion, and is not deteriorated by theendurance test and so on.

The second object of the present invention is to provide an air bag doorconstruction skin of which has excellent surface appearance, and inwhich the air bag develops smoothly and securely.

A skin of the present invention for overcoming the above problem or thesubject matter is comprised of a general portion and a defined portiondefined by an annular groove portion formed at a part of the generalportion, and having a parting line for parting the general portion andthe defined portion in the groove portion. Wherein the general portionhas an annular first bent portion formed along the groove portion toprotrude toward a rear surface to be inclined by a predetermined anglerelative to a surface of said general portion; the defined portion hasan annular second bent portion formed along the groove portion toprotrude toward a rear surface to be inclined by a predetermined anglerelative to a surface of the defined portion substantially parallel tothe first bent portion; and the surface of the first bent portion andthe surface of the second bent portion are closely opposed wherein thesurface of the general portion and the surface of the defined portionare flush with each other to form the groove portion therebetween.

A method for manufacturing a skin of the present invention manufacturesthe skin including a general portion and a defined portion defined by anannular groove formed at a part of the general portion. Themanufacturing method for the skin is comprised steps of preparing a moldhaving an endless and annular wall formed on a part of a moldingsurface; forming a skin including an annular groove portion ofsubstantially U-shape cross-section being formed by the wall of themold, the general portion located outside the groove portion, and adefined portion enclosed by the groove portion, and having a heightdifference or a step between a surface of the general portion and asurface of the defined portion; and then removing the height differencebetween the surface of the general portion and the surface of thedefined portion by relatively shifting the general portion and thedefined portion after separating the general portion and the definedportion by cutting a bottom portion of the groove portion.

A manufacturing method for a skin for an air bag door of the presentinvention for overcoming the above problem is comprised steps ofpreparing a mold having an endless and annular wall formed on a part ofa molding surface; forming a skin including an annular groove portion ofsubstantially U-shape cross-section being formed by the wall of themold, a general portion located outside the groove portion, and a doorportion enclosed by the groove portion, and having a height differenceor s step between a surface of the general portion and a surface of thedoor portion; and then removing the height difference between thesurface of the general portion and the surface of the door portion byrelatively shifting the general portion and the door portion afterseparating the general portion and the door portion by cutting a bottomportion of the groove portion.

An air bag door of the present invention for overcoming the aboveproblem includes a resin base member, a skin and an intermediate foamedbody layer, the skin including at a part thereof an annular grooveportion defining a general portion and a door portion and being provideda parting line where the skin is separated into the general portion andthe door portion. Wherein said general portion has an annular endportion having a first bent portion facing with the groove portion, andsaid door portion has an annular end portion having a second bentportion facing with the groove portion; and the first bent portion andthe second bent portion are inwardly inclined by a predetermined anglerespectively relative to the surface of the door portion so thatdiameters of the first bent portion and the second bent portion increasetowards the surface of the door portion, and are closely disposed to beburied in the foamed body layer.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view showing an air bag door part ofan instrument panel produced by the first embodiment of the presentinvention.

FIG. 2 is a partial cross-sectional view showing a powder slush moldused in the first embodiment of the present invention.

FIG. 3 is a partial cross-sectional view showing the powder slush moldon which a skin is formed in the first embodiment of the presentinvention.

FIG. 4 is a partial cross-sectional view showing the skin in a cut statein the first embodiment of the present invention.

FIG. 5 is an explanatory cross-sectional view showing a state where theskin is disposed on a molding surface of a foam mold in the firstembodiment of the present invention.

FIG. 6 is a partial cross-sectional view showing a powder slush moldused in the second embodiment of the present invention.

FIG. 7 is a partial cross-sectional view showing a skin produced by thesecond embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

In the skin of the present invention, the general portion and thedefined portion are separately formed and can be parted at the partingline formed in the annular groove portion. The general portion has theannular first bent portion formed along the groove portion to protrudetoward the rear surface to be inclined by the predetermined anglerelative to the surface of the general portion, and the defined portionhas the annular second bent portion formed along the groove portion toprotrude toward the rear surface to be inclined by the determined anglerelative to the surface of the defined parallel to the first bentportion. The surface of the first bent portion and the surface of thesecond bent portion are closely opposed to form the groove portiontherebetween, in the state where the surface of the general portion andthe surface of the defined portion are flush with each other.

That is, in the skin of the present invention, the depth direction ofthe groove portion is inclined relative to the skin surface.Accordingly, even when the groove portion of the skin is opened in theendurance test etc., only a inclined surface(s) of the first bentportion or the second bent portion appears. As a result, the grooveportion is observed to be shallow, and thus surface appearance of theskin is not deteriorated. In addition, since the general portion and thedefined portion are disposed in the separate state where the surface ofthe former and the surface of the latter are flush and the first bentportion of the former and the second bent portion of the latter areclosely contacted, stress has not been generated in the skin in theforming of the interior panel. Thus, the skin of the present inventioncan contribute to produce the interior panel in which no residual stresshas been existed and which has an excellent dimensional accuracy.

Here, the inclined directions of the first bent portion and the secondbent portion of the skin are not restricted. However, when the skin isused for the instrument panel having the air bag door, the first andsecond bent portions are preferably designed to be inclined by the acuteangles relative to the surface of the defined portion in order toprevent a mutual interference in the development of the air bag.

By the way, in the conventional manufacturing method of the air bag doorintegrate-type skin, there is a case where the surface of the air bagdoor and the surface of the interior panel are formed integrally andthen the door portion is formed by cutting the integrated skin along thecircle. When this manufacturing method is used, in order to conceal thecut end surface of the skin, an annular groove portion is preferablyformed at a boundary area between the door portion and the generalportion and then it is cut at a bottom portion thereof. However, whenthe annular groove portion is formed by a powder slush forming etc., themold needs to be provided with an annular wall on a molding surfacethereof. This wall should have thickness larger than the predeterminedvalue to maintain strength of the mold and so on. As a result, width ofthe groove portion of the skin increases unnecessarily, causing surfaceappearance deterioration of the skin surface.

In view of the above, in the manufacturing method for a skin of thepresent invention, a mold having an endless and annular wall formed on apart of a molding surface is prepared; and a skin including an annulargroove portion of substantially U-shape cross-section being formed bythe wall of the mold, a general portion located outside the grooveportion, and a defined portion enclosed by the groove portion, andhaving a height difference between a surface of the general portion anda surface of the defined portion is formed. Then the height differencebetween the surface of the general portion and the surface of thedefined portion is removed by relatively shifting the general portionand the defined portion after separating the general portion and thedefined portion by cutting a bottom portion of the groove portion.portion of substantially U-shape cross-section and formed by the wall ofthe mold, the general portion located outside the groove portion, andthe defined portion enclosed by the groove portion, and having a stepbetween a surface of the general portion and a surface of the definedportion is formed. Then, the step between the surface of the generalportion and the surface of the defined portion is removed by relativelyshifting the general portion and the defined portion after separatingthe general portion and the defined portion by cutting a bottom portionof the groove portion.

Working-out of the wall shape of the mold can narrow width of the grooveportion of the skin even if thickness of the wall is increased, so thatnot only strength of the mold can be secured but surface appearance ofthe skin can be improved.

In the manufacturing method of the skin of the present invention, thewall of the mold is preferably inclined by the predetermined anglerelative to the molding surface forming one of the general portion andthe defined portion of the skin. Cutting the bottom portion of thegroove portion formed by such inclined wall can form an annular firstbent portion bent toward the rear surface by a predetermined angle atthe end portion of the general portion facing with the groove portion,and can form an annular second bent portion bent toward the rear surfaceby a predetermined angle at the end portion of the defined portionfacing with the groove portion. In case where the whole annular wall ofthe mold is constructed into a truncated cone shape or a truncatedsquare pyramid shape by adjusting the inclined angle of the wall, whenthe step between the surfaces of the general portion and the definedportion of the skin is removed by relative shift between the generalportion and the defined portion, space existed between the first bentportion and the second bent portion can be narrowed. As a result, gapappeared at the boundary area between the general portion and thedefined portion can be narrowed, so that width of the groove portionformed between the first and second bent portions can be extremelynarrowed to increase surface appearance of the skin.

In addition, the whole wall of the mold can be constructed into arectangular shape having four sides a pair of wall parts of whichopposed to each other are inclined to be parallel. According to suchobstruction, shifting the general portion or the defined portion in thesame direction as the inclined direction of the wall can remove the stepbetween the surfaces of the general portion and the defined portion. Inthis case, working out the wall shape can shorten width of the grooveportion to almost zero in the surface observation, and width of at leastone paired opposing grooves will not be varied by the relative shiftbetween the general portion and the defined portion.

Hereinafter, embodying modes of the skin and the manufacturing methodthereof according to the present invention will be explained concretely.As the manufacturing method of the skin, a powder slush method and avacuum forming can be used. In the following, manufacturing of the skinby the powder slush forming method will be explained. It is notedhowever when the vacuum forming is used, the mold having the reversedconvex/concave on the molding surface to the convex/concave on themolding surface of the powder slush mold can be sufficiently used.

A height difference between the molding surface part for forming thegeneral portion and the molding surface part for forming the definedportion can be determined in view of the inclined angle of the wall. Forexample, the whole wall has substantially a reversed truncated coneshape in which diameter increases toward the molding surface, themolding surface is formed so that the molding surface part enclosed bythe wall becomes deeper than the molding surface part outside the wall.This mold can form the skin including the annular groove portion, thegeneral portion outside the groove portion and the defined portionenclosed by the groove portion, and having the step between the surfacesof the general portion and the defined portion. Then the general portionand the defined portion of the skin are separated by cutting the bottomportion of the groove portion, and are relatively shifted to remove thestep between the surfaces of the general portion and the definedportion. Consequently, in the relative shift of the general portion andthe defined portion, the first bent portion and the second bent portionare closely contacted to narrow width of the groove portion forming theboundary area between the general portion and the define portion. To thecontrary, the whole wall has a substantially truncated cone shape inwhich diameter decreases toward the molding surface, the molding surfaceis formed so that the molding surface part outside the wall becomesdeeper than the molding surface part enclosed by the wall.

In the above manufacturing method of the skin, the inclined angle of thewall relative to the molding surface is preferably selected larger than65 degrees. If the inclined angle of the wall is smaller than 65degrees, for example, angle difference between the abuse angle of thewall at side of the general portion and the acute angle of the wall atside of the defined portion increases. As a result, the difference ofradius of the round portion of the skin formed by the corner portions ofthe mold between the inside and outside of the wall increases, so thatsurface appearance of the skin is deteriorated.

The surface of the wall of the mold preferably protrudes from a moldingsurface (molding surface H) forming the skin having a higher surface,protrudes convexly following to the molding surface H, and then inversesto continue to a molding surface (molding surface L) forming the skinhaving a lower surface.

Such surface shape of the wall can, even if the tip end of the wall haslarge thickness, shorten distance between the first bent portion formedby the outer periphery surface at the tip end portion of the wall andthe second bent portion formed by the inner peripheral surface at theroot portion of the wall. Thus, width of the groove portion of the skincan be narrowed with securing strength of the wall of the mold.

Here, the skin manufactured by the above manufacturing method can beused as a skin for various vehicle interior goods such as an air bag,glove box door or console box door.

In case where the above manufacturing method of the skin is applied tothe skin for the air bag door, the wall of the mold is preferablyinclined inwardly relative to the molding surface part enclosed by thewall by the acute angle, more preferably by 65 to 85 degrees. Suchinwardly inclined wall can form the first bent portion and the secondbent portion of the skin of which the diameters increases toward thesurface side of the door portion, and of which the mutual interferencein the development of the air bag is avoided. Thus, scatter of the skinchip due to interference between the first and second bent portions canbe prevented.

The skin can be formed by resin materials such as polyvinylchloride,thermoplastic polyurethan or polyolefin.

The bottom portion of the groove portion can be cut by various cuttingmanners such as a blade, laser beam or water jet stream. When the bladeis used to cut the groove portion manually, it is guided by the sidewall of the wall to cut the bottom portion smoothly and accurately.

For manufacturing a skin integrated-type air bag door, the skin for theair bag door produced by the above manufacturing method for example isdisposed on one of molding surfaces of a foam molds so that the surfaceof the general portion and the surface of the door portion are flushwith each other. Such disposition of the surface skip can narrow gapbetween the first bent portion and the second bent portion, or can bringthe first bent portion and the second bent portion into a closelycontacted condition in the surface observation.

On the other hand, on other molding surface of the foam mold, the resinbase member having been formed into the predetermined shape by theinjection-molding etc. is disposed. In this condition, the foam formingis performed between the skin and the base member. Thus, the skinintegrate-type air bag door in which the skin and the base member arejoined to the foamed body layer can be produced. This manufacturingmethod can narrow gap between the first bent portion and the second bentportion of the skin sufficiently, so that not only leakage of thefoaming resin through the gap is prevented but the surface appearancedeterioration of the air bag door is prevented.

In this manufacturing method of the air bag door, the skin produced bythe above manufacturing method of the skin for the air bag door ispreferably used. However, the skin in which the general portion and thedoor portion are separately or independently formed, and which has thefirst bent portion and the second bent portion inclined by the sameangle can be used. Such skin can have the same advantage as above skin.

The tip end of the first bent portion and the second bent portion ispreferably covered by a tape etc. to prevent leakage of the foamingresin more securely. As the tape, tapes easily broken or torn in theexpansion of the air bag, not scattering chip thereof is preferablyused, and an urethan slub tape is most preferable for such tape. Theurethan slub tape becomes fragile by impregnation and solidification ofa foam urethan resin in the foam-forming to be easily broken. Aframework of the urethan foam can reduce scattering amount of the chip.

When the urethan slub tape is used, it preferably has width of about10.0 mm and preferably has small thickness of about 2.0 mm in view ofthe adhering work to the first and second bent portions. By takingeasiness for breaking of the tape in the expansion of the air bag intoconsideration, the porous tape having density of 0.01 to 0.2 g/cm³ isdesirably used in preference to the fiber series tape. An adhesive tapehaving adhesion at both surfaces thereof can be used to adhere theurethan slub tape to the tip end of the first and second bent portions,for example. However, when strength of a tape base member of theadhesive tape may affect bad influence to breaking character thereof, anadhesive agent can be used for adhesion of the urethan slub tape.

When the skin is disposed on the molding surface of the foam mold, it ispreferably held on the molding surface by an vacuum absorbing and so on.If the skin manufactured by the manufacturing method of the presentinvention is used, the whole surface of the skin can be made flat andthe groove portion formed between the general portion and the definedportion can be narrowed, by merely causing the relative shift betweenthe first bent portion and the second bent portion due to relativesliding therebetween. Accordingly, the skin can be positioned on themolding surface of the foam forming surface easily, and the man-hournecessary for positioning of the skin can be reduced due to even orsmooth surface shape (convex/concave are not formed).

As resin materials for the resin base member, hard resins such aspolypropylene, polyethylene, nylon, ABS resin, or reinforced resinproduced by mixing glass fibers into polypropylene etc. can beselectively used corresponding to the manufacturing cost and the formingmethod. In addition, the resin base member can be produced by theinjection-molding method and so on.

At a part of the resin base member corresponding to the door portion, afragile portion or an opening is formed. The fragile portion can beeasily broken or torn in expansion of the air bag. The fragile portioncan be formed by a groove, recessed portion, slit or penetrated hole.The fragile portion can have a square shape, U-shape, H-shape orcross-shape. The fragile portion of the resin base member and theboundary area (groove portion) of the skin between the general portionand the door portion can have same shape to be coincided at the sameposition, or can have different shape.

In the air bag door of the present invention, the general portion has anannular end portion having a first bent portion facing with the grooveportion, and the door portion has an annular end portion having a secondbent portion facing with the groove portion. The first bent portion andthe second bent portion are inwardly inclined by a predetermined anglerespectively relative to the surface of the door portion so thatdiameters of the first bent portion and the second bent portion increasetowards the surface of the door portion, and are closely disposed to beburied in the foamed body layer.

Therefore, extremely narrowed width of the groove portion givesexcellent surface appearance of the skin. The first bent portion and thesecond bent portion are not connected by the mechanical connection suchas engagement of the convex portion and the concave portion, so they canbe separated easily by the expanding force of the air bag, withouthindering development of the air bag and without scattering the skinchip in the tearing.

The inclined angle of the first bent portion and the second bent portiontoward the door portion is preferably selected more than 65 degrees. Ifthe inclined angles of the first bent portion and the second bentportion are smaller than 65 degrees, angle difference between the obtuseangle of the second bent portion and the acute angle of the first bentportion increases. As a result, the difference of radius of the roundportion of the skin formed by the corner portions of the mold betweenthe first bent portion and the second bent portion increases, so thatsurface appearance of the skin is deteriorated.

The first bent portion and the second bent portion are preferablyinclined relative to the surface of the door portion toward the innerperiphery side (radially inwardly) thereof, more preferably by angle of65 to 85 degrees. Such inclination of the first and second bent portionmakes opening of the air bag door in the expansion of the air bag easierfor allowing the air bag to develop into the vehicle room. The skin chipdue to interference between the adjacent skins will not be generated.

In summary, according to the skin of the present invention, it has thehigher dimensional accuracy of the skin and has the excellent surfaceappearance since deformation of the skin due to stress has not beenoccurred. If the groove portion of the skin is opened by in theendurance test etc., the surface appearance is not deteriorated.According to the manufacturing method for the skin of the presentinvention, the skin can be easily formed by single mold to reduce theman-hour and the manufacturing cost. Further, according to the air bagdoor of the present invention, it has the excellent surface appearancesince step between the general portion and the door portion is removedand width of the annular groove portion located at boundary of thegeneral portion and the door portion is extremely narrowed. Also, theair back door construction makes the air bag development easier, and itwill not scatter the skin chip in the air bag developing.

Preferred Embodiment of the Invention

Hereinafter, the present invention will be explained concretely based onembodiments in which the present invention has been applied to aninstrument panel of an automobile and to a skin thereof.

<Embodiment 1>

FIG. 1 shows a partial cross-sectional view showing an air bag door partfor an assistant seat of the instrument panel of this embodiment. Thisinstrument panel is constructed by a base member 1 made of a resinmaterial, a foamed body layer 2 laminated on a surface of the basemember 1 and made of a polyurethan foamed body, and a skin 3 laminatedon a surface of the foamed body layer 2.

A fragile portion 10 having an U-shape is formed on the base member 1 (abottom part of it is shown in FIG. 1), and a hinge portion 11 generallythin but thicker than the fragile portion 10 is formed between opposedends of the fragile portion 10. On a lower surface of the base member 1a tubular air bag containing portion 12 is formed below the fragileportion 10 to contain an air bag 4 therein.

The skin 3 is constructed by a general portion 30 forming most of theinstrument panel, and a door portion 31 having a circular or rectangularshape and positioned to face with the air bag containing portion 12, andan annular endless groove portion 32 is formed at a boundary areabetween the general portion 30 and the door portion 31. The generalportion 30 and the door portion 31 are separately formed, and thereforethe groove portion 32 has at a bottom portion thereof a parting linewhere the general portion 30 and the door portion 31 are to be parted orseparated. Along an end portion of the general portion 30 facing withthe groove portion 32 an annular first bent portion 33 is formed to bendtoward a rear surface of the general portion 30 by an obtuse anglerelative to a front surface thereof. Along an end portion of the doorportion 31 facing with the groove portion 32 an annular second bentportion 34 is formed to bend toward a rear surface of the door portion31 by an acute angle relative to a front surface thereof. The first bentportion 33 and the second bent portion 34 are closely contacted to eachother at opposing surfaces, and a urethan slub tape 6 covering a tip endof them is adhered thereto.

This instrument panel has been produced in the following steps. Firstly,the base portion 1 is formed by an injection-molding. The fragileportion 10, the hinge portion 11 and the air bag containing portion 12are formed simultaneous with forming of the base member 1.

FIG. 2 is a partial and enlarged cross sectional view showing a moldingsurface of a powder slush-mold 5 used to produce the skin 3. On amolding surface of the power slush mold 5, an annular wall 50 is formedto define an enclosing and protruded surface 51 and an enclosed andrecessed surface 52 recessed in a thickness direction of the mold 5. Thewall 50 has a substantially truncated square pyramid shape the diameterof which gradually decreases toward a tip end thereof, and is whollyinclined inwardly by 70 degrees relative to the recessed surface 52. Thewall 50 has a thickness of about 1 mm, and the protruded surface 51 andthe recessed surface 52 forms a step of about 2.9 mm height.

As thickness of the wall 50 decreases the step height between theprotruded surface 51 and the recessed surface 52 decreases, which isconvenient to reduce wasteful or useless amount of the skin 3 formed bythe mold 5. It is noted however, the wall 50 needs to have thicknessmore than 1 mm to secure desired strength of the mold 5.

The skin 3 is powder-slush-formed of a thermoplastic polyurethan powderby utilizing the powder slush mold 5. The skin 3 is formed, as shown inFIG. 3, to cover the wall 50, the protruded surface 51 and the recessedsurface 52 of the mold 5. On the skin 3, at position corresponding tothe wall 50 of the mold 5, an annular groove portion 35 havingsubstantially U-shape cross-section is formed.

Next, the skin 3 is demolded from the powder slush mold 5, and thegroove portion 35 is cut at the bottom portion thereof. As shown in FIG.4, cutting the groove portion 35 separates the skin 3 into the doorportion 31 and the general portion 30. At the end portion of the generalportion 30 facing with the door portion 31, the annular first bentportion 33 bent toward the rear surface by the obtuse angle relative tothe surface of the general portion 30 is formed, while at the endportion of the door portion 31 facing with the first bent portion 33 theannular second bent portion 34 bent toward the rear surface by the acuteangle relative to the surface of the door portion 31 is formed.

In the skin 3 thus produced, the door portion 31 and the general portion30 are relatively shifted so that the surface of the former and thesurface of the latter are flush with each other. Here, the first bentportion 33 and the second bent portion 34 gradually come close to eachother during the relative shift due to their inclinations, and arebrought into abutment at the time when the surface of the door portion31 and the surface of the general portion 30 are flush with each other.To a tip of the first bent portion 33 and the second bent portion 34,the urethan slub tape 6 is adhered to seal them.

Thereafter, as shown in FIG. 5, the skin 3 is subject to a vacuumabsorbing to be absorbed and held on one molding surface of a foam mold7. Here, the first bent portion 33 and the second bent portion 34 areclosely contacted to each other, so that the groove 32 formedtherebetween extends lineally and having an extremely small width. Theurethan slub tape 6 seals this linear groove 32.

In this condition, the base member 1 formed in advance is disposed onother molding surface (not shown) of the foam mold 7, and a foamingurethan resin is poured into a space formed between the skin 3 and thebase member 1. Thus, the foamed body layer 2 joined with the base member1 and the skin 3 integrally is formed. Here, the poured-in foamingurethan resin will not leak through the groove portion 32 since thefirst bent portion 33 and the second bent portion 34 are closelycontacted to each other and is covered by the urethan slub tape 6.

In the thus produced instrument panel, on a design surface of the skin3, the surface of the general portion 30 and the surface of the doorportion 31 flush with each other appear, and there is almost no fear ofresin leakage due to extremely small width of the groove portion 32. Inaddition, the first bent portion 33 and the second bent portion 34 areclosely contacted to each other in the separated condition, so anystress resulted from deformation of them will not occur in the first andsecond bent portions 33 and 34, whereby deformation of the skin 3 by thestress can be prevented. For this reason, the skin 3 is excellent insurface appearance and has smooth feeling. Further, even when the firstbent portion 33 and the second bent portion 34 are opened or spaced atthe groove portion 32 in an endurance test etc., only the surface of thefirst bent portion 33 inclined by obtuse angle is exposed but a deeperpart of the groove portion 32 inclined by acute angle is not exposed, sothat the surface appearance is not deteriorated.

In FIG. 1, when the air bag 4 contained in the air bag containingportion 12 of the base member 1 expands by shock applied to theautomobile, the base member 1 is torn along the fragile portion 10 andis rocked toward the foamed body layer 2 about the hinge portion 11 bythe expanding force of the air bag 4. The rocking force of the foamedbody layer 2 transmitted from the 3 base member 1 tears and opens thefoamed body layer 2 along a line corresponding to by the fragile portion10. By the tearing force from the foamed body layer 2, the skin 3 isgoing to be torn at the groove portion 32.

Here, the foaming urethan resin is impregnated into the urethan slubtape 6 and is solidified therein to make the urethan slub tape 6extremely fragile. In addition, the first bent portion 33 and the secondbent portion 34 are merely closely contacted. Accordingly, the skin 3can be easily parted into the first and second bent portions 33 and 34at the groove portion 32. In this way, the instrument panel comprised ofthe base member 1, the foamed body layer 2 and the skin 3 is torn andopened along the U-shape line to open the door portion 31 and the partof the base member 1 enclosed by the fragile portion 10 about the hingeportion 11, thereby allowing the air bag 4 to develop into the vehicleroom.

In addition, the first bent portion 33 and the second bent portion 34 ofthe skin 3 are inclined inwardly relative to the door portion 31 (towarda central portion of the door portion 31) by the angle of 70 degree, sothat the diameter or distance between the first and second bent portions33 and 34 increases toward the outside (upper surface in FIG. 1).Accordingly, the first and second bent portions 33 and 34 can guide theexpanding air bag 4 and will not scatter chip of the skin 3 due tonon-interference relation therebetween.

Here, in the instrument panel of this embodiment, the general portion 30and the door portion 31 of the skin 3 can be formed by the separate orindependent members. Here, the general portion 30 needs to be providedwith a hole portion having size corresponding to the door portion 31.

In this case, the instrument panel can be produced by the same processas the above instrument panel, except that cutting of the groove 35 ofthe skin 3 can be omitted by forming the first bent portion 33 and thesecond bent portion 34 on the general portion 30 and the door portion 31in advance. The general portion 30 and the door portion 31 arepreferably produced by the same or common mold, but can be produced bythe different or respective molds.

<Embodiment 2>

In the above embodiment 1, thickness of the wall 50 of the powder slushmold 5 can hardly be thinned smaller 1 mm, and therefore width of thegroove portion 35 of the skin 3 can hardly be narrowed furthermore.However, according to the following process for the air bag door part,even when the wall 50 of the mold 5 has the thickness larger than 1 mm,the general portion 30 and the door portion 31 of the skin 3 can beflush with each other, although some skin 3 is wastefully used.

That is, the embodiment 2 uses a powder slush mold 5 shown in FIG. 6 forforming the skin 3. On a molding surface of the powder slush mold 5, anannular wall 50 is formed to define at a part of the molding surfaceenclosed by the wall 50, and a recessed molding surface 52 (moldingsurface H) recessed relative the protruded surface 51 (molding surfaceL) is formed. The wall 50 is inclined inwardly by an acute anglerelative to the recessed molding surface 52 (molding surface H), andwholly has a substantially truncated square pyramid shape in whichdiameter of the wall 50 decreases toward a tip end thereof. At the tipend of the wall 50 a ring-like protruded portion 53 protruded radiallyinwardly is formed along a periphery of the recessed molding surface 52(molding surface H), while at a root portion of the wall 50 an annularrecessed portion 54 recessed radially outwardly is formed along theperiphery of the recessed molding surface 52. Such construction of themold 5 can not only shorten distance between the inner peripheralsurface of the recessed portion 54 and the outer peripheral surface ofthe wall 50, but can give the wall 50 a substantial thickness thereof tohave the sufficient strength.

Here, the angles determined by the both inner peripheral surfaces of therecessed portion 54 and the recessed molding surface 52 (molding surfaceH) are named θ_(1A) and θ_(1B) respectively. In this embodiment, theboth angles θ_(1A) and θ_(1B) are selected to be 75 degreesapproximately. When the both angles θ_(1A) and θ_(1B) are smaller than65 degrees, angle difference between the inclined angle (obtuse angle)of the wall 50 at side of the enclosing molding surface 51 (moldingsurface L) and the inclined angle (acute angle) of the wall 50 at sideof the recessed molding 52 surface (molding surface H) increases. As aresult, the difference of radius of the round portion of the skin 3formed by the corner portions of the mold 5 between the inside andoutside of the wall 50 increases, so that surface appearance of the skinis deteriorated. For this reason, the angles θ_(1A) and θ_(1B) arepreferably selected to be larger than 65 degrees, but smaller than 85degrees.

The skin 3 produced by this powder slush mold 5 is, as shown in FIG. 7,provided with an annular groove portion 35 having a substantiallyU-shape cross section at position corresponding to the wall 50 of themold 5. Cutting the groove portion 35 at a bottom portion thereof canseparate the skin 3 into the general portion 30 and the door portion 31of which surfaces can be flush with each other by relatively shiftingthe body portion 30 and the door portion 31 in the direction shown by anarrow A.

In the air bag door part of this embodiment, width of the groove portion35 to be formed between the general portion 30 and the door portion 31when the surfaces of them are flush can be extremely narrowed, withmaintaining strength of the wall 50.

In addition, since the wall 50 of the mold 5 are inclined inwardly bythe angles of θ_(1A) and θ_(1B) at the root portion thereof, the firstbent portion 33 and the second bent portion 34 of the skin 3 formed bythe mold 5 are inclined inwardly by approximately 75 degrees relative tothe surface of the door portion 31. For this inclination, diameter ordistance between the first and second bent portions 34 and 35 increasestoward the front (upper) surface of the door portion 31. Therefore, inthe air bag door construction produced by this skin 3, the air bag canexpand smoothly in the development thereof, and will not scatter chip ofthe skin 3 due to non-interference relation between the first and secondbent portions 33 and 34.

1. A vehicle interior article comprising a resin base member, a skin and an intermediate foamed body layer, said skin including at a part thereof an annular groove portion defining a general portion and a defined portion enclosed by the annular groove portion and being provided with a parting line where the skin is separated into the general portion and the defined portion, wherein: said general portion has an annular end portion having a first bent portion facing the groove portion, and said defined portion has an annular end portion having an annular second bent portion facing the groove portion; and wherein the second bent portion is inwardly inclined by an acute angle relative to the surface of the defined portion.
 2. A vehicle interior article according to claim 1, wherein said defined portion is an air bag door portion.
 3. A vehicle interior article according to claim 1, wherein said acute angle of the second bent portion relative to the surface of the defined portion is respectively selected to be 65 to 85 degrees.
 4. A vehicle interior article according to claim 1, wherein the inward inclination of the second bent portion, which is inwardly inclined by the acute angle respectively relative to the surface of the defined portion, is contiguous with the surface of the defined portion. 